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[Bug 881137] Re: UFW does not clean iptables setting from /etc/ufw/before.rules

 

As a workaround, add a flush for the nat chains you want flushed at
beginning of the section like this:

*nat
:PREROUTING ACCEPT [4:478]
:INPUT ACCEPT [4:478]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

-F POSTROUTING

-A POSTROUTING -o eth0 -j MASQUERADE
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT

Warrning: This WILL also delete rules which may have been put there by
other tools! ONLY do this if ufw is the only tool managing the specific
tables/ chains (here: nat POSTROUTING)

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https://bugs.launchpad.net/bugs/881137

Title:
  UFW does not clean iptables setting from /etc/ufw/before.rules

Status in ufw package in Ubuntu:
  Won't Fix

Bug description:
  Adding some additional settings to /etc/ufw/before.rules is not
  deleted when ufw is stopped.

  I added these lines at top of file /etc/ufw/before.rules

  *nat
  :POSTROUTING ACCEPT [0:0]
  -A POSTROUTING -o eth0 -j MASQUERADE
  COMMIT

  Then I reloaded ufw firewall with command: ufw reload. Output from
  iptables-save

  $ iptables-save -t nat
  *nat
  :PREROUTING ACCEPT [4:478]
  :INPUT ACCEPT [4:478]
  :OUTPUT ACCEPT [0:0]
  :POSTROUTING ACCEPT [0:0]
  -A POSTROUTING -o eth0 -j MASQUERADE 
  COMMIT

  Then I reloaded ufw firewall again:

  $ iptables-save -t nat
  *nat
  :PREROUTING ACCEPT [4:478]
  :INPUT ACCEPT [4:478]
  :OUTPUT ACCEPT [0:0]
  :POSTROUTING ACCEPT [0:0]
  -A POSTROUTING -o eth0 -j MASQUERADE 
  -A POSTROUTING -o eth0 -j MASQUERADE 
  COMMIT

  And ufw reload again

  $ iptables-save -t nat
  *nat
  :PREROUTING ACCEPT [4:478]
  :INPUT ACCEPT [4:478]
  :OUTPUT ACCEPT [0:0]
  :POSTROUTING ACCEPT [0:0]
  -A POSTROUTING -o eth0 -j MASQUERADE 
  -A POSTROUTING -o eth0 -j MASQUERADE 
  -A POSTROUTING -o eth0 -j MASQUERADE
  COMMIT

  And again and postrouting is never deleted when ufw is stopped and
  added again when stared. Same happen if I stop ufw firewall with: $
  stop ufw. nat lines are not cleaned.

  UFW should remove all iptables settings specified in config files
  after ufw is stopped! This can be dangerous if apt-get is updating
  some ufw files and scripts needs to reload ufw (some lines will be
  more times).

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